Voice-controlled two-way communication system



July 26, 1949. o. TSCHUMI LED TWO-WAY COMMUNICATION SYSTEM VOICE-CONTROL 2 Sheets-Sheet 1 Filed Jan 20, 1945 Fig I Evan/Z01 0, fscfi/zomz 2,477,275 VOICE-CONTROLLED TWO-WAY COMMUNICATION SYSTEM Filed Jan. 20, 1945 0. TSCHUMI July 26, 1949.

2 Sheets-Sheet 2 Patented July 26, 1949 UNITED STAT TENT OFFICE VDICE-CONTROLLED TWO-WAY COMMUNICATION SYSTEM land Application January 20, 1945, Serial No. 573,693 In Switzerland January 15, 1944 '7 Claims.

The invention relates to improvements in telephone systems for the transmission of voice signal current alternately in either direction and especially to systems of the type in which the direction of transmission is voice controlled.

Telephone systems in which the speaking direction can be changed by means of speech signals are well-known in the art. In some of these systems the first voice signal of a speech train serve for control purposes and are consequently lost from the conversation. Thisdisadvantage cannot be removed by making the control means more sensitive because the whole voice control system is then too exposed to disturbances.

The object of the invention is to provide a voice control telephone system for transmission of voice signal current alternately in either direction, wherein from the beginning of the first voice signal the whole speech train is transmitted uninterruptedly, that is wherein no voice signals are clipped from the speech train for control purposes. To attain this the control means according to the invention operates in such a way that the reversal of the direction of transmission is prepared during the transmission of the speech train and is carried out a predetermined time after cessation of this speech train. Because of the provided time delay no reversal is carried out following the short interruptions occurring in normal conversation.

A feature of the invention is to provide a telephone system of the kind mentioned wherein the voice control means iscombined with a manually operable control means for the reversing of the direction of transmission.

Other features and advantages of the invention will be apparent during the course of the following description.

In the accompanying drawings illustrating by way of example different embodiments of the telephone system according to the invention and in which like numerals are employed to designate like parts throughout the same,

Figure 1 shows an embodiment in which the control means according to the invention is arranged anywhere on the channel for transmitting the voice signal current connecting two subscribers either directly or by way of inter-connection devices;

Figure 2 shows an embodiment in which the control means are arranged at each subscriber station; I it Figure 3 shows an embodiment having further control means for reversing the direction of transmission, and

Figure 4 show the essential parts of another embodiment in which further control means are arranged permitting a subscriber to choose the speaking direction without regard to the existing operating condition.

Referring now to Figure 1, the conductor pairs an, In, and :12, in, forming the transmission channel connect the voice control means with the two subscriber stations. The voltage conditions are chosen so that opposite designated terminals have always the same potential (in and be; as and in). However, the polarity changes according to which station is adjusted to speaking.

On the one side a rectifier arrangement and, on the other side, the real reversal means are disposed at anyplace along these conductor pairs. The rectifier arrangement consists substantially of a direct current blocking condenser C2 to which the primary winding of transformer U is connected to the conductor pairs. The other winding is grounded at one end while the other end is connected to the grid of a rectifier tube R. The

reversal means includes a relay A having two coils (Al-2 and A34|) connected to different poles of a suitable electrical source and to the one or the other of the conductors according to the position of switches II2 and He. These two coils are arranged on the same-core (not shown) and operate a switch at, that is switch at is closed when one of the coils of relay Ais energized.

An auxiliary control circuit for controlling the reversing switches to I12, 116, includes two relays I and II, each having two coils (Ia, Ib and 11a, 1112, respectively) on a common core (not shown) operating on switch It and switches H4, H2, IIs, respectively. Thus, switch I4 is closed when current is fed through one or the other of the coils Ia and Ib, and'switches I12, H6, H4 are switched over from their positions as shown when current is fed through one or the other of the coils Ila and III). When both of the coils of these two relays I and II become currentless again, the respective switches fall back to their initial positions, as shown.

The auxiliary control circuit is connectable to ground by means of switch at and has two branches in parallel, one branch comprising in series switch I4, coil Ia of relay I and coil 11a of relay II, and the other branch comprising a switch sp t operated by a relay coil SP. The two parallel branches may be connected to either coil Ib or coil IIb and through these to the negative pole according to the position of switch Hi.

The rectifier tube R feeds the rectified speech signal current to the coil SP of a slow releasing relay connected to the anode of said tube, having a by-pass condenser Cl connected across its terminals. The illustrated system operates as follows:

While the subscriber at terminals al, bl converses with the subscriber receiving the transmitted speech signals at terminals a2, b2, the terminals al, b2 may be positive and the others, terminals (12, hi, may be negative, as shown. Under these conditions two separate circuits are closed through switches H2 or 11s, respectively, and the corresponding coils As-e and A14 of relay A, which are energized and close the switch ad in the auxiliary circuit. On the other hand the alternating current which is produced by the speech signals is applied to the grid of the rectifier tube B through the transformer 'U, thereby energizing releasing relay SP. The condense: C2 prevents any direct current short circuit oi the condenser pair. The excited, slow releasing relay SP closes the switch $134 so that a further circuit is closed through switches at, spll, I14 and relay coil Ib. Relay I is thereby energized and cioses switch I4, thereby effecting the closing of a new circuit through relay coils Ioand IIa. However, as long as the slow operating relay SP is energized, the relay coils Ia and 11a are short-circuited by the switch spt. The switch elements remain in this position as long as speech signals are uninter ruptedly emitted in the said direction. When the transmission of speech'signals is interrupted, the alternating current circuit is destroyed and the relay SP becomes dc-energized aiter a delay period determined by the decay of the charge on the condenser Cl. Within this delay time, that is before the relay SP is released, the converse" tion can be taken-up again by the subscriber in question in the same direction without effecting the change-over process. In consequence, the speaking direction can not be reversed merely by an ordinary interruption in conversation, but the reversal is dependent on the expiration of a time period of such a duration that this pause may be considered as an invitation to the conversing party to answer. When the slow operating relay SP becomes tie-energized. the switch so is opened and the circuit, including switch I4, coil Id of relay I, and coil IIa of relay II is no longer short-circulted. Thus, relay II is excited by means of its coil 11a and erects the switchover of the reverslngswitches'IIz and I16, and also of the switch IIt, so that a circuit is closed through the ground, switch (14, switch I4, relay coil Ia, relay coil 1112, switch I14, and relay coil 11b to the negative pole of the source. The arrangement remains in this condition until the second subscriber, whose station is now adjusted to transmission, begins to speak. Relay SP is again excited and switch sp l short-circuits relay coils Ia and 1m. The reversing switches I12, I16, and the switch I14 are retained in the same positionby the currentfiowing through relay coil IIb; switch I4, however, is opened as current is fed through neither of the coils Ia and lb of relay I. At the end of the speech train of the second subscriber and after the delay time of the slow releasing relay SP, switch S114 is opened, all auxiliary circuits are interrupted, and the relay coils 11a, 11b are de-energlzed whereby the switches II2, I16 and 11s return'to their initial position.

In this way the speaking direction is changed when the subscriber, whose station is connected for transmission, interrupts the voice signal current for a period exceeding the releasing time of the slow releasing relay. By this interruption the '4 reversing means are operated, which means were, however, already put into condition preparatory to the reversion of the direction of transmission by a relay energized by the voice signal current, but were at the same time blocked by this relay from carrying out the reversal to its final end.

Referring now to Figure 2, the two subscriber stations Si and S2 each have their own control means and consist substantially of the transducers LM and of the amplifiers V with the reversing switches WI and W2 which are under the influence of relay W in such a way that they are only operated when the armature of this relay W is released. The voice controlled slow releasing relay SP controls the switch 3194. L designates the two-wire conductors joining the two stations. Figure 2 illustrates the working condition existing when station SI is adjusted for transmission and station S2 for reception. The emission of the speech signals in the indicated direction causes the excitation of relay SP; switch spa is closed and relay W energized. After the emission ceases and the delay time of relay SP has expired, this relay is de-energized, and after the opening of switch sp t, relay W is also de-energized, whereby the switches WI and W2 are changed over and the speaking direction is reversed. This process is repeated whenever the switch relay W is de-energized, that is any time the relay W releases its armature the reversing contacts W l and W2 are operated. This is accomplishedwhenever the emission of speech signals is interrupted for a time interval exceeding the delay period of the voice controlled relay SP.

In this embodiment the position of the voice controlled relays is immaterial. They may be arranged either in the output of the amplifier (as shown) or in the line, for instance, connected to the point K of each subscriber station.

The embodiment shown in Figure 3 presents further reversing possibilities of the speaking direction as they are, for instance, described in patent application Serial No. 535,297, now U. S.

Patent No. 2,460,475, granted Feb. 1, 1949. The condenser pairs a|, bl, and :12, b2 are connected to the transformer'U, whose middle winding is grounded at one end and has its other end connected to the voice controlled relay SP by means of a switch d and the rectifier tube R. The centers of the outer windings of the transformer U are alternately connected through the reversin switches I2 or Is, respectively, and relay coils J and Y to sources of positive and negative potential, respectively.

The auxiliary control circuit includes four branches connected in parallel on one side to ground, and on the other side through switch I14 and either coil ID of relay I or coil 11b of relay II to the negative pole of an electrical source. The first branch comprises in series (just as in the embodiment of Figure 1) the switch It operated when one of the coils Ia or II) is current fed, coil IIa of relay 11a and coil Ia of relay I. In this case the reversing switches I2 and I5 are operated at the same time as switch I4 upon energizing of the coils Ia or 1b of relay I. The second and third branch comprise in series a switch a or b, respectively, operated by relays not shown, and a switch it or g4, respectively, operated by relays J or Y, respectively. The switches a and b remain closed on the establishment of a connection between the two subscriber stations; the switches i4 and yd are kept in open position as long as the relays I and Y, respectively, are current fed, but are closed when these relays are released. The fourth branch comprises in series a switch spI4 operated by a slow releasing relay SPI, which is on one side connected to the nega tive pole of a source, and a switch spfl operated by the slow releasing relay SP, which is connected to the anode of the rectifier tube R. When the relay SP is energized by the voice signal current, the switch sp4 connects the relay SPI to ground, whereas on releasing of relay SP the switch sp connects this fourth branch to ground. This embodiment of the invention operates as follows:

The operating condition speaking or listening of a station is determined bythe position of the reversing switches I2 and I6. As illustrated. in the pending application Serial No. 535,297, a change-over of the speaking direction can also be obtained by the listening subscriber. This is accomplished by operating for a short time certain switching means (not shown), whereby either relay J or relay Y is de-energized, and the switches id or 114, respectively, which are normally open during operation, are closed sothat through the also closed switches a and b, relay coil Ib is energized and the reversing switches I2 and Is are switchedover under the influence of relay coil Ib, thereby changing the direction of transmission. Switch 14', which is closed at the same time, Works as a holding key in order to maintain the excitation of relay I through its coil Ia when, after a short period of interruption, relay J or Y, respectively, is again energized. By the closing of switch I4, relay coil IIa is current fed so that as a permanent condition'a circuitfrom ground through switch I4, relay coils 11a and Ia, switch H4 and relay coil 11b to the negative potential is established. A new, short-period interruption in the circuit of the relays J or Y, respectively, again causes the closing of the switch it or switch g4, whereby the relay coils Ia and Her are shortcircuited so that relay I is released and the switches I2, I4, Is,- fall back to their previous position while relay II releases its switch II4 after reopening of switch i l or g4, respectively.

In this way the reversal of the direction of transmission of the voice signal current is carried out by the operation of switch means belonging to the subscribers.

The speaking direction may also be reversed by the voice signal current itself, through the excitation of the control relay SP, which thereby changes over its switch sp; consequently, the slow releasing relay SPI is energized thereby closing the switch spI4. As soon as the emission of speech signals is lacking beyond the delay period of the slow releasing relay SP, this relay SP is released and its switch $104 falls back to close the circuit through switches sp l, spI4, 114., and relay coil Ib to the negative potential source. The switch spI4 of the slow releasing relay SPI is released after a certain time interval when the current through coil Ib has already energized relay I to reverse the switches I2 and Is and to close the holding switch I4. Relay II is also energized and causes the reversing of switch I14. In this way the same processes are the same as in the first case in which the branch line, including switches sp l and $1014 takes the place of the branch including switches a, 1 4 or b, it, respectively. The second change-over and thereby re-= establishment of the first operating condition is obtained analogously to the change-over already described in that owing to the breaking-oil of the next speech train the two relay coils Ia and Her are short-circuited by the closing of the switches $104 and $1214.

As'follows from the above, the voice controlled device according to the invention can be formed in such a way that besides the pure voice control, it allows in addition the control by means .of mechanically operated means belonging to a subscriber.

Figure 4 shows the essential part of an embodiment of the invention wherein control means are arranged at each subscribers station by means of which each subscriber may reverse the direction of transmission of the voice signal current without regard to the existing operating condition. 'The drawing shows the subscribers station adjusted to speakingcomprising the transducer LM, the amplifier V with input transformer EU and output transformer AU, and the reversing switches I12 and H6 determining the speaking direction. The station is connected to the transmission channel ab and thereby to the other-station by means of a transformer LU. A valve R is connected between the amplifier V and transformer LU by means of key T2. Coupled to the anode of valve R are two relays FI and FII in series and parallel to these two relays an arrangement of a metal rectifier bridge with a slow releasing relay SP. The coils of the relays FI and F11 are tuned to a certain frequency and operate switches II and in.

The auxiliary control circuit corresponds substantially to that illustrated in Figure 1, that is it has two parallel branches, one comprising in series switch I4 operated by coils Ia or Ib of relay I, coil Ia of relay I, and coil 11a of relay II; the other branch comprising switch sp operated by the slow releasing relay SP. These two parallel branches are connectedon. the one hand to ground through switch e, whichis kept closed during operation, and key TI, and on the other hand by means of switch II4 operated by coil Hit or coil III) of relay II to either coil Ib or coil IIb and to the negative pole of an electrical source. Parallel to coil III) are arranged the grounded switches ]I and fill. This embodiment operates as follows:

As soon as speech signals are emitted, relay SP is energized over the closed key T2 and the valve R so that switch spd is closed. Switch e and key Tl being closed, relay coil Ib is energized effecting a closing of switch I4, and consequently the ener gizing of relay II through its coil IIa, resulting in the reversing of switches I14, 112, and IIs, as soon as switch spa interrupts the short circuit of relay coil that is as soon as at the end of a speech train the delayed period of the. slow releasing voice control relay SP has expired. All this and also the changing back to the initial positions of the several switches takes place in the same manner as is described in connection with Figure 1. The embodiment shown, however, allows each subscriber, in whatever operating condition his station may be, to establish on his own initiative, in his station the speaking and in his partners station the listening condition. The establishment of the speaking condition in his own station can be carried out by operating the keys Ti and T2 in the sense of a short-period interruption, advantageously by a common key. With regard to the key Tl, this interruption causes the release of .all relays of the auxiliary circuit and, thereby, the reversing ofthe switches I12 and Us from the listening position to the speaking position, while by the corresponding operation of the contact T2 the voice controlled relay SP is de-energized, so that after the shortperiod interruption the connection corresponds to that shown in the drawing. In order to establish the listening condition in the partners station, the emission of a special alternating current impulse is necessary, either by transmitting a voice frequency signal amplified by the amplifier, or in another way. It is advantageous to couple the corresponding transmission means for the control impulse with the common key controlling the keys Ti and T2. This alternating current impulse flows through the coils of the relays l d and PH of the partners station, which coils are tuned to the selected frequency. The energizing of these relays operating on the switches II and III, respectively, causes in the auxiliary control circuit, which is in the "speaking condition, a closing of an additional circuit from ground through switches f1 and HI and relay coil 11?) to the negative potential source, whereby relay II is excited and made to adjust the station in question to the listening condition.

What I claim is:

1. In a telephone system, a channel for transmitting voice signal current alternately in either direction, means for reversing the direction of transmission of said voice signal, an auxiliary control circuit for actuating said reversing means including a relay operable to put said auxiliary circuit into a condition preparatory to effecting a reversal of the direction of transmission of said voice signal current, and a slow releasing relay coupled with said channel and energized by the voice signal current to close a circuit for switching the contacts of said first mentioned relay into a position to put said auxiliary circuit into a con dition preparatory to efiecting a reversal of the direction of transmission, said slow releasing relay releasing a predetermined time after cessation of a speech train to complete the reversal of the direction of transmission.

2. In a telephone system with a channel for transmitting voice signal current alternately in either direction according to claim 1, means for reversing the direction of transmission of said voice signal, an auxiliary control circuit for actuating said reversing means, and a slow releasing relay coupled with said channel and energized by the voice signal current arranged at each subscriber station.

3. In a telephone system, a channel for transmitting voice signal current alternately in either direction, means for reversing the direction of transmission of said voice signal current, an auxiliary control circuit connectable to an electrical supply source for actuating said reversing means, including two relays, one of which operates said reversing means and each having two separate coils, said auxiliary control circuit having two branches connected in parallel, which branches are connectable in series to either a coil of the one or a coil of the other of said relays alternately by means of a switch operated by one of said relays, one of said parallel branches comprising in series a switch operated by the relay different from said relay operating the first mentioned switch, and the other two coils of said two relays, the other branch comprising a switch operated by a slow releasing relay which is coupled with said channel and energized by the voice signal current to put said auxiliary circuit into a condition preparatory to effecting a reversal of the direction of transmission, said slow releasing relay releasing said switch a predetermined time after cessation of a speech train to complete the reversal of the direction of transmission.

4. In a telephone system, a channel for transmitting voice signal current alternately in either direction, means for reversing the direction of transmission of said voice signal current, an auxiliary control circuit connectable to an electrical supply source including two relays, one of which operates said reversing means and each having two separate coils, said auxiliary control circuit having two branches connected in parallel which are connectable in series to either a coil of the one or a coil of the other of said relays alternately by means of a switch operated by the first mentioned relay in such a way that said switch connects said coil of the said first relay to said parallel branches when one of the coils of this'first relay is energized and connects the said coil of said other, second, relay to said parallel branches when said first relay is released, one of said parallel branches comprising in series a switch closing when said second relay is energized, and the two other coils of said two relays, and the other branch comprising a switch operated by a slow releasing relay coupled by means of a rectifier device with said channel, said switch closing when said slow releasing relay is energized by the voice signal current and opening a predetermined time after cessation of a speech train.

5. In a telephone system, a channel for transmitting voice signal current alternately in either direction, means for reversing the direction of transmission of said voice signal current, an auxiliary control circuit connectable to an electrical supply source including two relays, one of which operates said reversing means and each relay having two separate coils, said auxiliary control circuit having four branches connected in parallel which are connecta-ble in series to either a coil of the one or a coil of the other of said relays alternately by means of a switch operated by one of said relays, one of said parallel branches comprising in series a switch operated by the relay different from said relay operating the first mentioned switch and the other two coils of said two relays, the second and third of said branches each including a switch associated with one of two relays respectively, the coils of which are arranged in circuits connecting said channel with an electrical supply source, said last mentioned switches serving for manually reversing the direction of transmission, and the fourth branch including a switch associated with a slow releasing relay which is coupled with said channel and energized by the voice signal current to put said auxiliary circuit into a condition preparatory to efiecting a reversal of the direction of transmission, said slow releasing relay releasing said switch a predetermined time after cessation of a speech train to complete the reversal of the direction of trans mission.

6. In a telephone system, a channel for transmitting voice signal current alternately in either direction, means for reversing the direction of transmission of said voice signal current, an auxiliary control circuit connectable to an electrical supply source, including two relays, one of which operates said reversing means, each relay having two separate coils, said auxiliary control circuit having four branches connected in parallel, which branches are connectable in series to either a coil of the one or a coil of the other of said relays alternately by means of a switch operated by the relay difierent from said first mentioned relay operating the reversing means in such a way that said switch connects the coil of the second mentioned relay to said parallel branches when one of the coils of the second relay is energized and connects the said coil of said first mentioned relay to said parallelbranches when said second relay is released, one of said parallel branches comprising in series a switch closing when said first relay is energized and the two other coils of said two relays, the second and third of said branches each including a switch associated with one of two relays respectively arranged in circuits connecting said channel with an electrical supply source in such a Way that said last mentioned switches are closed when said last mentioned relays are temporarily released, and the fourth branch comprising in series two switches, one belonging to a slow releasing relay and opening a certain time interval after said slow releasing relay is de-energized, the other switch belonging to a second slow releasing relay coupled by means of a rectifier device with said channel, said other switch connecting said first slow releasing relay to an electrical supply source when said second slow releasing relay is energized by the voice signal current and closing said fourth branch, thereby disconnecting said first slow releasing relay a predetermined time after cessation of a speech train.

7. In a telephone system, a channel for transmitting voice signal current alternately in either direction, means for reversing the direction of transmission of said voice signal current, an auxiliary control circuit connectable to an electrical supply source arranged at each subscriber station, said control circuit including two relays, one of which operates said reversing means and each having two separate coils, said auxiliary control circuit having two branches connected in parallel which are connectable in series with either a coil of the one or a coil of the other of said relays alternately by means of a switch operated by the first mentioned relay in such a way that said switch connects said coil of said first relay to said parallel branches when one of the coils of this first relay is energized and connects the said coil 10 of said other, second, relay to said parallel branches, when said first relay is released, one of said parallel branches comprising in series a switch closing when said second relay is energized, and the other two coils of said two relays and the other branch comprising a switch operated by a slow releasing relay coupled with said channel by means of a rectifier bridge, said last mentioned switch closing when said slow releasing relay is energized by the voice signal current and opening a predetermined time after cessation of a speech train, said parallel branches being connected to the electrical supply source and said rectifier bridge being connected to said channel through manually operable switches for reversing the direction of transmission in a subscriber station from listening to speaking by opening these switches for a short-time interval, and at least one relay with a coil tuned to a certain frequency being connected parallel to said rectifier bridge, which last mentioned relay operates a corresponding switch arranged in a circuit comprising an electrical supply source and the first mentioned coil of said first relay for reversing the direction of transmission in a subscriber station from speaking to listening by energizing said tuned relay coil with a current oithe said certain frequency and thereby closing said last mentioned switch.

OTTO TSCHUMI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,102,903 Leveque Dec. 21, 1937 2,162,370 Campbell June 13, 1939 2,192,540 Creti Mar. 5, 1940 2,236,645 Levy Apr. 1, 1941 2,282,405 Herrick May 12, 1942 

